As an important basic chemical raw material, aromatic hydrocarbons are mainly used in the production of chemical products such as chemical fibers, plastics and rubber. With the rapid development of petrochemical and textile industries and the continuous development of textile industry, the global demand for the aromatic hydrocarbons is increasing with time. At present, industrial production of the aromatic hydrocarbons mainly comes from oil and coal. The way to take the oil as raw material includes reforming production of refineries, gasoline pyrolysis of ethylene plants and toluene disproportionation, and the way to take the coal as raw material mainly comes from coal coking. However, the reserves of fossil resources such as coal and oil are limited, so it is of great significance to develop the route to obtain the aromatic hydrocarbons from non-fossil resources. CO2, as the cheapest and most abundant resource in the carbon family, is abundant on earth. With the continuous development of human society, the use amount of the fossil energy has increased sharply, and the content of CO2 in the atmosphere has increased with time, which not only aggravates the greenhouse effect, but also causes a huge waste of carbon resources. The CO2 captured in industrial waste gas or atmosphere is used for the production of hydrogen from renewable energy sources; and a circulation mode for preparing liquid hydrocarbon through CO2 catalytic hydrogenation is conducted, which is of great significance to solving two new challenges of climate change and energy crisis in human society.
The research shows that the preparation of hydrocarbons by CO2 hydrogenation usually takes two steps. First, CO2 is subjected to reversed water gas shift reaction to produce CO, and then CO is subjected to Fischer-Tropsch synthesis to form the hydrocarbon compounds. In the traditional Fischer-Tropsch synthesis process of CO hydrogenation to produce hydrocarbons, the product selectivity is limited by the anderson-schulz-flory (ASF) rule. According to the ASF distribution, the maximum selectivity of C5-C11 hydrocarbons is only 45%. Unlike CO hydrogenation, because CO2 is slow in absorption on a catalyst surface, in the CO2 hydrogenation, C/H ratio on the catalyst surface is low. This phenomenon is conducive to the surface adsorption of species for hydrogenation and reducing the chain growth probability of products, thereby improving the methane selectivity. However, it makes it more difficult for CO2 hydrogenation to prepare long-chain hydrocarbons. Therefore, at present, the target products researched in CO2 hydrogenation are mainly methanol (such as CN201110006073.8) dimethyl ether (such as CN201410495290.1), methane (such as CN201210444697.2) and low-carbon olefin (such as CN201510102620.0) and other small molecular weight hydrocarbons or oxygen containing compounds, while there are few studies on the preparation of long chain hydrocarbons by CO2 hydrogenation. Literature (Y. Tan et al. Ind. Eng. Chem. Res. 38(1999) 3225-3229) reports that when Fe—Zn—Zr/HZSM-5 composite catalyst is used and CO2 conversion rate is about 19.5%, C5+ hydrocarbon selectivity can reach 52%, but the selectivity of the side product CO can reach 57.4% and C5+ yield is very low. Recently, M. Fujiwara, et al. (Appl. Catal. B: Environ 179 (2015) 37-43) has found that the Cu—Zn—Al methanol synthesizing catalyst is mixed with modified HB molecular sieve to obtain a composite catalyst, and C2+ hydrocarbon can be obtained by CO2 hydrogenation, but the selectivity of the side product CO is higher than 50%.
The efficiency of CO2 hydrogenation to directly produce liquid hydrocarbons is low, and especially for aromatic hydrocarbons as part of liquid hydrocarbons, the efficiency is lower (the selectivity of the side product CO and the selectivity of methane are too high), which is also an important reason that there is no report about CO2 hydrogenation to efficiently prepare the aromatic hydrocarbons. Therefore, how to find a technical route for efficient production of the aromatic hydrocarbons by CO2 hydrogenation has become a great challenge in the field of CO2 conversion and utilization.